Update diag convenience methods

diag/diagnostic.go

@@ -93,14 +93,6 @@ func (d Diagnostic) Validate() error {
 	return nil
 }
 
-// FromErr will convert an error into a Diagnostic
-func FromErr(err error) Diagnostic {
-	return Diagnostic{
-		Severity: Error,
-		Summary:  err.Error(),
-	}
-}
-
 // Severity is an enum type marking the severity level of a Diagnostic
 type Severity int
 

diag/helpers.go

@@ -0,0 +1,36 @@
+package diag
+
+import "fmt"
+
+// FromErr will convert an error into a Diagnostics. This returns Diagnostics
+// as the most common use case in Go will be handling a single error
+// returned from a function.
+//
+//   if err != nil {
+//     return diag.FromErr(err)
+//   }
+func FromErr(err error) Diagnostics {
+	return Diagnostics{
+		Diagnostic{
+			Severity: Error,
+			Summary:  err.Error(),
+		},
+	}
+}
+
+// Errorf creates a Diagnostics with a single Error level Diagnostic entry.
+// The summary is populated by performing a fmt.Sprintf with the supplied
+// values. This returns a single error in a Diagnostics as errors typically
+// do not occur in multiples as warnings may.
+//
+//   if unexpectedCondition {
+//     return diag.Errorf("unexpected: %s", someValue)
+//   }
+func Errorf(format string, a ...interface{}) Diagnostics {
+	return Diagnostics{
+		Diagnostic{
+			Severity: Error,
+			Summary:  fmt.Sprintf(format, a...),
+		},
+	}
+}

helper/schema/provider.go

@@ -243,12 +243,9 @@ func (p *Provider) ValidateResource(
 //
 // This won't be called at all if no provider configuration is given.
 func (p *Provider) Configure(ctx context.Context, c *terraform.ResourceConfig) diag.Diagnostics {
-
-	var diags diag.Diagnostics
-
 	// No configuration
 	if p.ConfigureFunc == nil && p.ConfigureContextFunc == nil {
-		return diags
+		return nil
 	}
 
 	sm := schemaMap(p.Schema)
@@ -257,31 +254,30 @@ func (p *Provider) Configure(ctx context.Context, c *terraform.ResourceConfig) d
 	// generate an intermediary "diff" although that is never exposed.
 	diff, err := sm.Diff(ctx, nil, c, nil, p.meta, true)
 	if err != nil {
-		return append(diags, diag.FromErr(err))
+		return diag.FromErr(err)
 	}
 
 	data, err := sm.Data(nil, diff)
 	if err != nil {
-		return append(diags, diag.FromErr(err))
+		return diag.FromErr(err)
 	}
 
 	if p.ConfigureFunc != nil {
 		meta, err := p.ConfigureFunc(data)
 		if err != nil {
-			return append(diags, diag.FromErr(err))
+			return diag.FromErr(err)
 		}
 		p.meta = meta
 	}
 	if p.ConfigureContextFunc != nil {
-		meta, ds := p.ConfigureContextFunc(ctx, data)
-		diags = append(diags, ds...)
+		meta, diags := p.ConfigureContextFunc(ctx, data)
 		if diags.HasError() {
 			return diags
 		}
 		p.meta = meta
 	}
 
-	return diags
+	return nil
 }
 
 // Resources returns all the available resource types that this provider

helper/schema/provider_test.go

@@ -144,7 +144,7 @@ func TestProviderConfigure(t *testing.T) {
 						return nil, nil
 					}
 
-					return nil, diag.Diagnostics{diag.FromErr(fmt.Errorf("nope"))}
+					return nil, diag.Errorf("nope")
 				},
 			},
 			Config: map[string]interface{}{

helper/schema/resource.go

@@ -266,11 +266,10 @@ type CustomizeDiffFunc func(context.Context, *ResourceDiff, interface{}) error
 
 func (r *Resource) create(ctx context.Context, d *ResourceData, meta interface{}) diag.Diagnostics {
 	if r.Create != nil {
-		var diags diag.Diagnostics
 		if err := r.Create(d, meta); err != nil {
-			diags = append(diags, diag.FromErr(err))
+			return diag.FromErr(err)
 		}
-		return diags
+		return nil
 	}
 	ctx, cancel := context.WithTimeout(ctx, d.Timeout(TimeoutCreate))
 	defer cancel()
@@ -279,11 +278,10 @@ func (r *Resource) create(ctx context.Context, d *ResourceData, meta interface{}
 
 func (r *Resource) read(ctx context.Context, d *ResourceData, meta interface{}) diag.Diagnostics {
 	if r.Read != nil {
-		var diags diag.Diagnostics
 		if err := r.Read(d, meta); err != nil {
-			diags = append(diags, diag.FromErr(err))
+			return diag.FromErr(err)
 		}
-		return diags
+		return nil
 	}
 	ctx, cancel := context.WithTimeout(ctx, d.Timeout(TimeoutRead))
 	defer cancel()
@@ -292,11 +290,10 @@ func (r *Resource) read(ctx context.Context, d *ResourceData, meta interface{})
 
 func (r *Resource) update(ctx context.Context, d *ResourceData, meta interface{}) diag.Diagnostics {
 	if r.Update != nil {
-		var diags diag.Diagnostics
 		if err := r.Update(d, meta); err != nil {
-			diags = append(diags, diag.FromErr(err))
+			return diag.FromErr(err)
 		}
-		return diags
+		return nil
 	}
 	ctx, cancel := context.WithTimeout(ctx, d.Timeout(TimeoutUpdate))
 	defer cancel()
@@ -305,11 +302,10 @@ func (r *Resource) update(ctx context.Context, d *ResourceData, meta interface{}
 
 func (r *Resource) delete(ctx context.Context, d *ResourceData, meta interface{}) diag.Diagnostics {
 	if r.Delete != nil {
-		var diags diag.Diagnostics
 		if err := r.Delete(d, meta); err != nil {
-			diags = append(diags, diag.FromErr(err))
+			return diag.FromErr(err)
 		}
-		return diags
+		return nil
 	}
 	ctx, cancel := context.WithTimeout(ctx, d.Timeout(TimeoutDelete))
 	defer cancel()
@@ -322,12 +318,9 @@ func (r *Resource) Apply(
 	s *terraform.InstanceState,
 	d *terraform.InstanceDiff,
 	meta interface{}) (*terraform.InstanceState, diag.Diagnostics) {
-
-	var diags diag.Diagnostics
-
 	data, err := schemaMap(r.Schema).Data(s, d)
 	if err != nil {
-		return s, append(diags, diag.FromErr(err))
+		return s, diag.FromErr(err)
 	}
 
 	if s != nil && data != nil {
@@ -358,11 +351,12 @@ func (r *Resource) Apply(
 		s = new(terraform.InstanceState)
 	}
 
+	var diags diag.Diagnostics
+
 	if d.Destroy || d.RequiresNew() {
 		if s.ID != "" {
 			// Destroy the resource since it is created
 			diags = append(diags, r.delete(ctx, data, meta)...)
-
 			if diags.HasError() {
 				return r.recordCurrentSchemaVersion(data.State()), diags
 			}
@@ -380,7 +374,7 @@ func (r *Resource) Apply(
 		// Reset the data to be stateless since we just destroyed
 		data, err = schemaMap(r.Schema).Data(nil, d)
 		if err != nil {
-			return nil, append(diags, diag.FromErr(err))
+			return nil, diag.FromErr(err)
 		}
 
 		// data was reset, need to re-apply the parsed timeouts
@@ -485,18 +479,14 @@ func (r *Resource) ReadDataApply(
 	d *terraform.InstanceDiff,
 	meta interface{},
 ) (*terraform.InstanceState, diag.Diagnostics) {
-
-	var diags diag.Diagnostics
-
 	// Data sources are always built completely from scratch
 	// on each read, so the source state is always nil.
 	data, err := schemaMap(r.Schema).Data(nil, d)
 	if err != nil {
-		return nil, append(diags, diag.FromErr(err))
+		return nil, diag.FromErr(err)
 	}
 
-	diags = append(diags, r.read(ctx, data, meta)...)
-
+	diags := r.read(ctx, data, meta)
 	state := data.State()
 	if state != nil && state.ID == "" {
 		// Data sources can set an ID if they want, but they aren't
@@ -517,12 +507,9 @@ func (r *Resource) RefreshWithoutUpgrade(
 	ctx context.Context,
 	s *terraform.InstanceState,
 	meta interface{}) (*terraform.InstanceState, diag.Diagnostics) {
-
-	var diags diag.Diagnostics
-
 	// If the ID is already somehow blank, it doesn't exist
 	if s.ID == "" {
-		return nil, diags
+		return nil, nil
 	}
 
 	rt := ResourceTimeout{}
@@ -537,7 +524,7 @@ func (r *Resource) RefreshWithoutUpgrade(
 		// affect our Read later.
 		data, err := schemaMap(r.Schema).Data(s, nil)
 		if err != nil {
-			return s, append(diags, diag.FromErr(err))
+			return s, diag.FromErr(err)
 		}
 		data.timeouts = &rt
 
@@ -547,26 +534,25 @@ func (r *Resource) RefreshWithoutUpgrade(
 
 		exists, err := r.Exists(data, meta)
 		if err != nil {
-			return s, append(diags, diag.FromErr(err))
+			return s, diag.FromErr(err)
 		}
 
 		if !exists {
-			return nil, diags
+			return nil, nil
 		}
 	}
 
 	data, err := schemaMap(r.Schema).Data(s, nil)
 	if err != nil {
-		return s, append(diags, diag.FromErr(err))
+		return s, diag.FromErr(err)
 	}
 	data.timeouts = &rt
 
 	if s != nil {
 		data.providerMeta = s.ProviderMeta
 	}
 
-	diags = append(diags, r.read(ctx, data, meta)...)
-
+	diags := r.read(ctx, data, meta)
 	state := data.State()
 	if state != nil && state.ID == "" {
 		state = nil